Apparatuses permitting survey and treatment of a surface, or predetermined zones of this surface, are of increasing interest in the field of survey and maintenance of steam generators of nuclear power stations, particularly for inspection of steam generator tubes.
In a general manner, a vehicle provided with progression means of the caterpillar type allows displacement of a probe-carrying tool in front of the openings of the tubes of the steam generator, the caterpillar having for example spigots able to be engaged in the mentioned orifices in order to ensure progression of the assembly constituted by the vehicle and the probe-carrying tool. Such apparatus has been described particularly in French Patent Application No. 2 471 026 published on 12th June 1981.
Although such systems give satisfaction for the survey and/or maintenance of surfaces provided with openings arranged at a very regular pitch, the pitch of the spigots of the caterpillar being correspondingly arranged, they cannot be used in the case of smooth surfaces and particularly curved surfaces.
In the technical field of survey and/or maintenance of steam generators for nuclear power stations, it is necessary to provide systems for survey and/or treatment of both curved and flat smooth surfaces. In particular, it is indispensable, preliminarily to the bringing into service of the nuclear reactor, to carry out electrochemical polishing of the internal walls of the water box of the steam generator, which essentially consist of curved, spherical or flat smooth surfaces.
This polishing is necessary in order to reduce the susceptibility to contamination of these walls by fixing, in the absence of polish, of radioactive erosion products such as contaminating oxides coming from the central part of the reactor and carried by the steam generator water and thus to reduce the risks of exposure to these contaminating products of maintenance staff brought in to carry out systematic periodic maintenance. This polishing can also be carried out either in a preventative manner, as previously described, or in a curative manner, after a number of hours of functioning of the reactor.